AU2013220406B2

AU2013220406B2 - Process and device for fixed-bed pressure gasification of solid fuels

Info

Publication number: AU2013220406B2
Application number: AU2013220406A
Authority: AU
Inventors: Martin Grabner; Bernd Meyer
Original assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 2012-02-13
Filing date: 2013-02-13
Publication date: 2015-12-24
Anticipated expiration: 2033-02-13
Also published as: IN2014DN06625A; RU2014137020A; ZA201406700B; AU2013220406A1; CN204111704U; KR102054353B1; DE102013202356A1; UA112216C2; KR20140131358A; WO2013120917A1; RU2607662C2; AP2014007913A0

Abstract

The invention relates to a process and a device for fixed-bed pressure gasification of solid fuels having an increased performance and also a widened usage spectrum of solid fuels. For this purpose, the process is conducted in such a manner that, using a fixed-bed pressure gasifier with a feed of the coarse-grain solid fuels and with a gas take off, both at the top of the fixed-bed pressure gasifier, with a rotary grid and with ash discharge at the bottom of the fixed-bed pressure gasifier, with an adjustable feed for first gasification agent for a non-slagging gasification using the rotary grid of the fixed-bed pressure gasifier, wherein critical minimum values for the steam-oxygen ratio can be set, having a heap of the fixed bed above the rotary grid, in addition to the first gasification agents fed using the rotary grid, second gasification agents for a slagging gasification are injected via at least one gasification agent nozzle extending into the upper region of the fixed-bed heap.

Description

I PROCESS AND APPARATUS FOR THE FIXED-BED PRESSURE GASIFICATION OF SOLID FUELS 1. FIELD OF THE INVENTION 5 This invention relates to a process and an apparatus for the fixed-bed pressure gasification of solid fuels with increased performance and a widened usage spectrum of solid fuels. Processes and apparatuses according to the invention allow the gasification of coals with a higher fine grain content and/or in addition the gasification of fine-grained and pulverized fuels. 10 2. BACKGROUND TO THE INVENTION The gasification of coarse-grained solid fuels, i.e. of coarse-grained coals and/or carbonaceous solids with grain sizes greater than about 5 mm and smaller than about 10 mm, preferably is effected in the fixed bed by the process of fixed-bed 15 pressure gasification FPG, also known under the term Fixed Bed Dry Bottom Gasification. The fuels are introduced into the fixed-bed pressure gasifier over head by means of pressure locks. In the fixed bed (actually moving bed), which extends over the height of the fixed-bed pressure gasifier, the following zones are formed in an ideal-typical way from top to bottom: Drying zone, pyrolysis zone, 20 gasification zone, oxidation zone and ash zone. At the bottom of the gasifier the ashes are discharged through a rotary grate which at the same time serves for supplying the gasification media. The raw gas draw is located at the top of the fixed-bed pressure gasifier. 25 The gasification media substantially consist of technical oxygen and steam. The latter is added in excess, in order to limit the maximum temperatures in the oxidation zone to values below or in the vicinity of the ash melting temperatures relevant for the fixed-bed pressure gasification and thus avoid the formation of massive, interfering ash agglomerates or slaggings (non-slagging gasification). 30 The quantity ratio of steam and oxygen in the gasification medium represents one of the most important quantities for the control of the process. It frequently is indicated as steam/oxygen ratio, preferably in the units kg steam/mtd 3 oxygen (100 vol-%). Depending on the height of the ash melting temperatures, minimum 2 values between about 4 kg/m 3 (high-melting ashes) and about 9 kg/m 3 (low melting ashes) are required. The steam excesses increase the gas flow velocities and the amount of fine grain which is discharged with the raw gases via the raw gas outlet, but do not contribute to an increase of the reaction turnover. Although 5 the values for the steam/oxygen ratio are adapted to the ash melting temperatures and are kept as low as possible (critical minimum values of the steam/oxygen ratio for a so-called "hot" operation at the "slag limit"), this results in considerable limitations above all with respect to the maximum performance, the permeability of the bed and the discharge of dust, see also /J. Schmalfeld: Die 10 Veredlung und Umwandlung von Kohle, DGMK (2008), p. 311/. A general disadvantage of the fixed-bed pressure gasification, which is caused thereby, consists in that the solid fuels to be gasified should contain only small amounts of fine-grained fuels with grain sizes smaller than about 5 mm and in 15 particular pulverized fuels with grain sizes smaller than about 1 mm. Otherwise, this results in local accumulations of fine-grained material in the fixed bed with the consequence of a non-regular, channel-like flow through the fixed bed as well as a high discharge of dust, incomplete carbon conversions in the ashes or slaggings. These negative effects are reinforced in different ways, when caking 20 hard coals or briquetted lignites are used. The general disadvantage of the counterflow principle furthermore applies for the low raw gas outlet temperatures of the fixed-bed pressure gasification. Ammonia, non-condensable higher hydrocarbons, phenols and tar oils, which together with 25 the discharged dusts are separated in the water (tar/gas water/dust mixtures), generally are undesired by-products. The raw gas outlet temperatures are obtained in dependence on the feed fuels corresponding to the total heat balance of the process. Except for the selectively arranged, incomplete heat exchange between gas and solids (e.g. lowered bed) they cannot be increased actively. 30 To maintain the required grain size spectrum of the coarse-grained fuels to be gasified, the raw coals mined must be processed. In particular, hard coals are screened and/or washed before the gasification, in order to separate the fine 3 grain (coal fines), lower the ash content, and increase the quality of the solid fuels to be gasified. The fines smaller than 5 mm frequently amount to up to 50 % of the unscreened, mined coal. Since the separated coal fines cannot easily be utilized for the production of synthesis gases during the fixed-bed pressure 5 gasification, corresponding solutions were sought. According to patent document EP10792A1 pellets were formed from the fine grained fuels, which are surrounded by a non-caking enveloping layer. Patent document GB1435089A describes the production of a fine coal/ash/pitch mixture 10 which is processed in an extruder to obtain extrudates and from the extruder is pressed directly into the free gas space of the atmospherically operated fixed-bed pressure gasifier. As pelletizing aids for coal fines bentonites also are proposed (US patent 4,773,919 B1). Alternatively, US patent 4,146,369 BI provides to expand the fixed-bed pressure gasifier towards the top by a fluidized-bed gasifier 15 and above the same by an entrained-flow gasifier, in which fine-grained and pulverized fuels should be usable. There is also proposed a separate arrangement of fluidized-bed or entrained-flow gasifiers for processing the fine grained or pulverized fuels, e.g. in patent document WO 1980/00974 Al the gasification of a previously produced fuel/hydrocarbon/water slurry in the 20 entrained-flow gasifier. Patent document DD 219 597 Al discloses a process for the non-slagging gasification of coals, in which the feed of gasification medium is split up into a primary and a secondary feed. At a freely selectable bed height adjusted to the 25 material to be gasified, the main part of the gasification medium is supplied to the primary gasification separate from the grate and the part to be gasified provided for the secondary gasification is supplied via the grate in a known way, wherein the steam/oxygen ratio should be reducible down the to exclusive injection of steam. In general, this is a non-slagging operation of the gasification with the 30 formation of fine-grained ash. According to the proposal, the gasifier must be operated with high steam/oxygen ratios, so as not to exceed the ash melting point. The reason is to avoid slaggings of the gasifier. In general, the fine ash constituents should quickly be transported into the region below the gasification 4 medium exit, in order to avoid an ash transport into the upper reactor sections and the discharge of ash with the production gas. It should be noted that the proposal disregards the elementary requirements of environmental protection, of the efficiency and the operational safety. The major to complete feed of the 5 gasification medium into the higher regions of the bed at a non-slagging operation of the gasifier necessarily leads to burning through of the bed (channel breakthrough) and the mixture of not completely reacted oxygen with the raw gas, so that deflagrations or explosions can occur with catastrophic consequences. Further reasons for the unfeasibility of the proposal are the incompleteness of the 10 carbon conversion, i.e. the high carbon content of the ash withdrawn via the rotary grate, and the prevention of the suitability of the ash for landfill disposal. A further procedural limitation of the non-slagging fixed-bed gasification according to the prior art relates to the fuel spectrum with respect to the caking capacity of 15 the coals. Hard coals with stronger caking properties can be gasified, but require a mechanical stirrer in the upper part of the fixed-bed pressure gasifier, whereby the process as a whole becomes more complicated, more susceptible to failure and more expensive. 20 It has not been possible so far to find procedurally more favorable solutions for the omission of the stirrer. The other proposed solutions for the utilization of fine fuels are technically expensive and economically not viable. They could not gain acceptance in practice. The fine coal must be supplied to another use (in general the combustion) instead of the gasification. Nevertheless, a large part of the fine 25 coal frequently is not economically usable and must be deposited in the form of heaps, In light of the above, it would prove beneficial to develop a process for the fixed bed pressure gasification with an associated apparatus, which by means of small 30 procedural and technical changes as compared to previously known fixed-bed pressure gasifiers allow to increase the performance of the fixed-bed pressure gasifiers, to lower the use of steam, to widen the spectrum of use of the fuels with 5 respect to caking coals and coals with a higher fine grain content and/or in addition to gasify fine-grained and pulverized fuels. 3. SUMMARY OF THE INVENTION 5 The present invention, in one aspect, provides a process for the fixed-bed pressure gasification of coarse-grained, solid fuels with oxygen- and steam containing gasification media by means of a fixed-bed pressure gasifier with a feed of the coarse-grained, solid fuels and with a gas draw, both at the top of the fixed-bed pressure gasifier, with a rotary grate and with an ash discharge at the 10 bottom of the fixed-bed pressure gasifier, with an adjustable feed for first gasification media for a non-slagging gasification by means of the rotary grate of the fixed-bed pressure gasifier, wherein critical minimum values for the steam/oxygen ratio can be adjusted, with a heap of the fixed bed above the rotary grate, 15 - wherein in addition to and independent of the first gasification media supplied by means of the rotary grate second gasification media for a slagging gasification are injected via at least one gasification media nozzle reaching into the upper region of the fixed-bed heap, - and wherein the second gasification media are injected with steam/oxygen 20 ratios of 0.5 to 4 kg/m 3 and gas exit velocities of 20 to 120 m/s. According to this aspect of the invention, second gasification media for the slagging gasification are supplied to the fixed-bed pressure gasifier in addition to and independent of the first gasification media supplied via the rotary grate for the 25 non-slagging gasification. The second gasification media are advantageously injected into the upper region of the heap of the fixed bed by means of gasification media nozzles reaching into the upper region of the fixed-bed heap. With the first gasification media the first non-slagging gasification with the ideal typical formation of zones is carried out over the entire heap of the fixed bed (first 30 drying zone, first pyrolysis zone, first gasification zone, first oxidation zone, first ash zone), and with the second gasification media the second slagging gasification with local formation of turbulent zones (raceway formation) is carried out.

6 The critical minimum values for the steam/oxygen ratios (indicated in the units kg steam/md3 oxygen (100 vol-%) of the first gasification media for the "hot" operation at the "slag limit" are adapted to the ash melting behavior of the solid 5 fuels used. In simple terms, the adaptation is effected such that a rather defined ash granulation is effected (softening and sintering of the ash), without the occurrence of slaggings and the formation of large slag lumps which block the discharge, cf. /J. Schmalfeld: Die Veredlung und Umwandlung von Kohle, DGMK (2008), p. 311/. 10 Advantageously, the second gasification media are injected into the upper half of the first gasification zone formed during the gasification, i.e. below the first pyrolysis zone formed during the gasification. What is particularly advantageous is the injection of the second gasification media in a height zone which comprises 15 a vertical extension of < I m in the upper half of the first gasification zone below the pyrolysis zone. Particularly advantageously, the second gasification media are injected in a height zone of the fixed-bed pressure gasifier which maximally extends from 1 m above the tip of the rotary grate to 0.5 m below the surface of the heap of the fixed bed, preferably from 2 m above the tip of the rotary grate to 20 1 m below the surface of the heap of the fixed bed. According to an advantageous aspect of the process of the invention, the quantity of the injected oxygen of the second gasification media corresponds to 0 to 50 % of the total oxygen quantity supplied. 25 The injection of the second gasification media with gas exit velocities of 20 to 120 m/s causes the formation of turbulent raceways in the form of cavities in the fixed bed heap before the outlet openings of the gasification media nozzles in which carbon is burnt with oxygen (second combustion zones). The turbulent zones 30 before the nozzles are enveloped by a heap of coke with which the excess steam of the first non-slagging gasification and possibly the steam of the second slagging gasification react with a decrease in temperature (second gasification zones).

7 Due to the fact that the second gasification media are injected with steam/oxygen ratios with values of 0.5 kg/mstd 3 to 4 kg/mstd 3 , preferably of 0.5 to 3 kg/mstd 3 , it is achieved that the ashes released before the at least one gasification media 5 nozzle reaching into the upper region of the fixed-bed heap melt or sinter immediately and are deposited in the coke heap at the edge of the turbulent zones (second slag zones). The molten or sintered ashes quickly cool down and solidify in the surrounding colder coke heap and release their heat to the surroundings for reinforcing the endothermal second gasification processes. The 10 formation of classical, layer-shaped zones does not occur during the gasification with the second gasification media. For example, with the second gasification media with steam/oxygen ratios of 0.5 mean maximum temperatures of about 2000 *C are achieved before the 15 gasification media nozzles reaching into the fixed-bed heap, which is advantageous for the gasification of coals with ash melting points of 1500 - 1700 C. When the steam/oxygen ratio of the second gasification media is 3.0, mean maximum temperatures of about 1800 OC are achieved before the gasification media nozzles reaching into the fixed-bed heap. This is advantageous for the 20 gasification of coals with ash melting points of 1300 - 1500 OC. It is advantageous when the gasification with the second gasification media is carried out below the first pyrolysis zone. It is ensured here that degassed coke is available (higher cold gas efficiency as compared to coal) and the slags or sinter 25 formed solidify quickly in the surrounding colder coke heap. On the other hand, as will be explained below, the ambient temperatures of about 800 to 1100 'C in the surroundings of the gasification media nozzles reaching into the fixed-bed heap are so high that the solidified slags do not yet obtain a high strength. Slags adhering to the gasification media nozzles are detached from the heap moving 30 downwards and are transported further on. With respect to the temperatures of the coke heap in the first gasification zone the following should be noted: Due to the endothermal gasification reactions (initially 8 without taking account of the second gasification processes), the temperatures of the coke heap settle at approximately constant values of the so-called kinetic reaction end temperatures. These values are obtained automatically, chiefly in dependence on the reactivity of the cokes with respect to steam. The range of the 5 reaction end temperatures extends from about 800 'C with high-reactivity fuels (e.g. ortho-lignites) to 1100 "C with low-reactivity fuels (e.g. low-volatility bituminous hard coals). Thus, it lies below the temperature range for the ash melting points of most fuels (about 1200 - 1500 *C). 10 It is particularly advantageous that the ashes released during the second slagging gasification melt immediately and suppress each channelling, since a channel-like "burn-through" of oxygen through the heap is inhibited due to the immediate formation of slag. Initially formed channels or channels which originate from the first gasification likewise are quickly "closed" by forming slag. For this reason, the 15 turbulent zones cannot be removed from the gasification media nozzles towards the top or only to a small extent, but meander at approximately the same height before and above the gasification media nozzles. The second gasification hence is locally limited and defined in height corresponding to the arrangement of the outlet openings of the gasification media nozzles. The meandering gas flow and 20 the slag formed stabilize the fixed bed in the surroundings of and above the gasification media nozzles, so that despite higher flow velocities the regular flow through the fixed bed is maintained. The second slagging gasification leads to a uniformization of the flow through the 25 entire fixed bed. The fine grain content of the used coarse-grained fuels can be increased without the discharge of dust with the raw gases rising. The lower grain sizes of the coarse-grained solid fuels supplied to the fixed-bed pressure gasifier at the top can be lowered from about 5 mm to about 2 mm. 30 Due to the gasification with the second gasification media for the slagging gasification, fine-grained and/or pulverized fuels (fine fuels) can be utilized in larger amounts in addition to the coarse-grained fuels, which otherwise would have to be supplied to another use or dumping. For this purpose, the fine fuels 9 are introduced into the turbulent zones in concentrated form, wherein the quantities of the added fine fuels at most are so large that in stoichiometric terms a substantial gasification in the turbulent zones is ensured. 5 Another advantage of the second slagging gasification consists in that in particular the fine-grained and pulverized parts of the fuels are gasified in the turbulent zones by producing coarser ash/slag particles. The cooled, solidified slags contribute to increasing the grain size in the entire fixed bed, in particular in the first ash zone, and furthermore to the "interlocking" stabilization of the fixed 10 bed over the entire height. Local accumulations of fine grain and dust, which cause an eruption-like flow through the bed and are one of the main causes for high discharges of dust, are inhibited or pushed back. The second gasification thus leads to a uniformization of the flow through the entire fixed bed. The fine grain content of the fuels used can be increased without the discharge of dust 15 with the raw gases rising. Dry to moist, flowable fine fuels advantageously are charged into the heap of the fixed bed from above by means of gravity, approximately vertically above the turbulent zones formed before the gasification media nozzles. On gravity input, 20 the fuels slip into the gasifier due to their own weight via a dosing device, from a pressure lock arranged above the fixed-bed pressure gasifier. What is also possible, however, is a gravity input or a pressure input from the side directly into the fixed bed above the turbulent zones. Dry, pneumatically conveyable fine fuels also are blown directly into the turbulent zones by means of pneumatic 25 conveyance via the gasification media nozzles or from the side. Finally, fine fuels in the form of slurries are pumped in, namely either via the gasification media nozzles or approximately vertically above the turbulent zones from above onto or into the heap of the fixed bed. 30 Alternatively, the use of a stuffing input also is possible, which is effected at the upper edge of the fixed bed, preferably within the first drying zone. By means of a briquetting press, preferably a stamp press, fine-grained and/or pulverized fuels (fine fuels) are compressed, partly agglomerated or compacted in a mold channel 10 and pressed directly into the bed. In contrast to the teaching of patent document GB1 435089A, the compacted fine fuels do not fall onto the fixed bed from above, whereby a crumbling of the compacted fine fuels followed by an increased discharge of dust in the raw gas is avoided. At the same time, the entering strand 5 of compacted fine fuels is covered towards the top by coarse-grained fuels, so that a direct blow-out of the abrasion is prevented. Another essential advantage of this input system is the possible admixture of the tar-oil solids mixture obtained as agglomeration aid during the fixed-bed pressure gasification and the possible omission of a lock system for the input of the fine fuels. Due to the very high 10 compacting pressures up to 150 MPa, which occur in the mold channel, an almost gas-tight closure between the pressurized gasification space and the surroundings is possible under atmospheric pressure, so that a separate pressurizing system of the fine fuels can be omitted. This form of the input of fine fuels is independent of the operation of the second gasification and can also be 15 employed with non-operated or disused second gasification media nozzles. The second slagging gasification not only improves the fuel tolerance with respect to increased fine-grain and dust contents of the fuels or provides for the additional input of fine fuels, but it also increases the fuel tolerance with respect to caking 20 coals, which would not be gasifiable without the use of a stirrer. The second combustion zones with their fast rises in temperature and their high temperatures reduce the caking tendency of the coals and break up coke bonds formed already. Due to the second slagging gasification, the use of the stirrer can be omitted in many cases. 25 It is also possible to carry out the second slagging gasification in the first pyrolysis zone or in the region of the transition from the first pyrolysis zone to the first non slagging gasification zone. In this case, the ratio of the combustion and gasification reactions is shifted more in direction of combustion reactions in the 30 second slagging combustion zones. The raw gas outlet temperatures rise and the higher hydrocarbons, phenols as well as tar oils, which leave the fixed bed towards the top, are thermally broken down more strongly. The zone-related adjustment of the second slagging gasification is achieved by setting defined bed 11 heights of the fixed bed. In this way, the raw gas outlet temperatures and the quality of the raw gas (methane content, undesired secondary components, etc.) can be adapted. 5 The gasification media nozzles are designed as water-cooled gasification media mixture nozzles (in the case of oxygen and steam as second gasification media) or as water-cooled multicomponent nozzles (in the case of the combined feed of fine fuels). They can be both non-cranked (tubular nozzles) and cranked (crank nozzles), wherein in the case of the crank nozzles the cranked nozzle head is 10 seated on the tubular nozzle shank. The gasification media nozzles are guided through the cylindrical outer jacket or double jacket of the fixed-bed pressure gasifier. The non-cranked gasification media nozzles are aligned radially and horizontally or different from the radial and 15 horizontal alignment attachable in all directions with angles of attack of < 45'. Preferably, the nozzles are aligned radially and inclined downwards by 10 to 20* against the horizontal. This is found to be advantageous with respect to the avoidance of the entry of solids into the interior of the nozzles and with respect to the formation of the turbulent zones. In the case of the use of cranked gasification 20 media nozzles, the nozzle shanks are aligned approximately horizontally and the nozzle heads analogous to the above-mentioned angles of attack of the tubular nozzles. The second slagging gasification is carried out in a limited height zone in the 25 upper region of the bed of the fixed-bed pressure gasifier. The lower limitation is given by the fact that a sufficient large, vertical minimum distance to the underlying oxidation zone is ensured. This distance is > 0.5 m, preferably > 1 m. The vertical minimum distance to the tip of the rotary grate hence is > 1 m, preferably > 2 m. It is required to allow the slag or sinter formed in the turbulent 30 zone to solidify, before it gets into the oxidation zone or onto the surface of the rotary grate. On the other hand, the gasification media nozzles are not exposed to too high temperatures (< 1100 *C) in the gasification zone. The upper limitation of the height zone results from the fact that a sufficiently high overlap of the 12 gasification media nozzles by the fuel layer of the fixed bed of > 0.5 m, preferably > 1 m, is ensured. With a bed height of the fixed bed of 5 m, calculated from the tip of the rotary grate, the vertical extension of the height zone for the second gasification can amount to a maximum of 3.5 m, preferably a maximum of 2 m. 5 The gasification media nozzles can be distributed over this height and over the cross-section of the fixed-bed pressure gasifier. Another advantageous aspect consists in that for the second slagging gasification zone a rather short height zone with a vertical extension of < 1 m in the upper half 10 of the first gasification zone, below the pyrolysis zone, is chosen, so that the first non-slagging gasification zone is extended towards the top uniformly over the cross-section. In case the height of the heap of the fixed bed is changed during the operation of 15 the fixed-bed pressure gasifier between a maximum and a minimum level and the difference is more than 1 m, it is advantageous when alternatively two height zones of the fixed-bed pressure gasifier are equipped with gasification media nozzles, the lower height zone for the minimum level and the upper height zone for the maximum level of the fixed bed. The vertical minimum distance of the two 20 height zones is more than 1 m. In procedural terms, the two height zones then are selectively charged with the second gasification media. Advantageously, the second gasification media are injected in a height zone either in a planar, horizontal plane, in a vertically stepped arrangement in the 25 height zone, or in a cone-shaped height zone which approximately reproduces the mushroom-shaped contour of the rotary grate or the contour of the bed surface. Preferably, the nozzle orifices of the gasification media nozzles are located in a 30 height zone either in a planar, horizontal plane, in a vertically stepped arrangement in the height zone, or in a cone-shaped height zone which approximately reproduces the mushroom-shaped contour of the rotary grate or the contour of the bed surface.

13 With a free length of at least 10 cm (free nozzle lengths), the gasification media nozzles protrude into the gasification space of the fixed-bed pressure gasifier. Preferably, the gasification media nozzles located close to the wall protrude about 5 20 cm to 1 m into the gasification space of the fixed-bed pressure gasifier, With larger, free nozzle lengths up to about 3 m, the gasification media nozzles are held from above by means of tie rods. To form turbulent zones locally separated from each other, the lateral, horizontal 10 distance between the outlet openings of the gasification media nozzles should not fall below 50 cm. Preferably, the lateral, horizontal distance of the outlet openings is I to 2 m. The vertical distance of outlet openings located one above the other should be at least I m, preferably however greater than 2 m. 15 The second gasification media are injected with steam/oxygen ratios between 0.5 and 4 kg/m 3 , preferably between 0.5 and 3 kg/m 3 . Although no steam is required from a procedural point of view, a small admixture of steam is advantageous, so that when the oxygen is shut off fast, steam is available as purge gas for the gasification media nozzles without interruption. Instead of steam, carbon dioxide 20 or other inert gases also can be used as purge gases. The quantity ratios of second to first oxygen can be varied within wide limits. In the case of an individual gasification media nozzle, 5 to 20 wt.-% of the entire oxygen supplied are injected as second oxygen. The upper value also can be 25 exceeded when larger amounts of fine fuels should be utilized with a gasification media nozzle. In the case of the formation of a second gasification zone over the entire cross-section of the fixed-bed pressure gasifier and the additional gasification of fine fuels, up to 50 wt.-% of the entire oxygen supplied can be injected as second oxygen. The lower the ash contents of the feed fuels, the 30 higher amounts of second oxygen are achievable. The size of the slag or sinter pieces formed in the turbulent zones before the individual gasification media nozzles is limited by the fact that the oxygen loads of 14 the individual gasification media nozzles are varied between minimum and maximum load. The total oxygen quantity of the second gasification media can be kept constant by varying the load distribution between the individual nozzles, or the total oxygen quantity also can be varied over time. 5 Corresponding to the quantity ratios of second oxygen (for the sagging gasification) injected in addition to the first oxygen (for the non-slagging gasification), the thermal capacities of the fixed-bed pressure gasifier are increased approximately proportionally. It is of minor importance whether the fuel 10 throughput is increased or whether additional fine fuels are introduced. Together with the coarse-grained fuels or in addition to the coarse-grained fuels, larger amounts of fine-grained and fine fuels can be gasified. The fuel spectrum also can be expanded in direction of hard coals caking more strongly, without the use of a stirrer being required. At the same time, the specific use of steam is lowered, 15 and the performance limit of the thermal gasifier capacity is increased due to the improved flow conditions of the heap of the fixed bed. Also described herein is a fixed-bed pressure gasifier for gasifying coarse grained, solid fuels with oxygen- and steam-containing gasification media with a 20 feed of the coarse-grained, solid fuels and with a raw gas draw, both at the top of the fixed-bed pressure gasifier, with a rotary grate and with an ash discharge at the bottom of the fixed-bed pressure gasifier, with an adjustable feed for first gasification media for a non-slagging gasification by means of the rotary grate of the fixed-bed pressure gasifier, wherein critical minimum values for the 25 steam/oxygen ratio are adjustable, with a heap of the fixed bed above the rotary grate, wherein at the level of the upper region of the fixed-bed heap the fixed-bed pressure gasifier includes at least one gasification media nozzle protruding into the upper region for an additional and independent feed of second gasification media as compared to the first gasification media for a non-slagging gasification, 30 wherein the at least one gasification media nozzle is designed such that it allows the injection of second gasification media with steam/oxygen ratios of 0.5 to 4 kg/m 3 , preferably of 0.5 to 3 kg/M 3

.

15 According to an advantageous aspect of the fixed-bed pressure gasifier, the at least one gasification media nozzle is designed such that the quantity of the injected oxygen of the second gasification media corresponds to 0 to 50 % of the total oxygen quantity supplied. 5 Advantageously, the fixed-bed pressure gasifier includes several gasification media nozzles for the second gasification media, which are arranged in one or two planes. 10 According to an advantageous aspect, the fixed-bed pressure gasifier includes at least one inlet for fine-grained and/or pulverized fuels (fine fuel inlet). The fine fuel inlet is designed as gravity inlet or as stuffing inlet for fine fuels compacted by briquetting. 15 According to an advantageous aspect of the fixed-bed pressure gasifier, the gasification media nozzles are designed as water-cooled gasification media mixture nozzles (in the case of oxygen and steam as second gasification media) or as water-cooled multicomponent nozzles (in the case of the combined fine fuel supply). Preferably with a free length of at least 10 cm (free nozzle lengths), the 20 gasification media nozzles protrude into the gasification space of the fixed-bed pressure gasifier. According to an advantageous aspect of the invention, the nozzle orifices of the gasification media nozzles in one height zone are located either in a planar, 25 horizontal plane, in a vertically stepped arrangement in the height zone, or in a cone-shaped height zone which approximately reproduces the mushroom-shaped contour of the rotary grate or the contour of the bed surface. The technical design of the second slagging gasification is simple, robust and 30 requires only minor technical adaptations of the known and well-tried fixed-bed pressure gasifier. The same concern the lead-through stubs for the gasification media nozzles and, if necessary, the supply stubs for the fine fuels. It is found to be particularly advantageous that the second slagging gasification in existing 16 plants of the fixed-bed pressure gasification can be set up, retrofitted and operated incrementally (starting with one gasification media nozzle) to completely (with a complete set of gasification media nozzles), or can be operated partly or be put out of operation or be backfitted corresponding to the requirements. 5 With reference to the attached drawings, a non-limiting embodiment of the invention will be described below in further detail. 4. BRIEF DESCRIPTION OF THE DRAWINGS 10 Fig. I shows a schematic diagrammatic longitudinal section of a fixed-bed pressure gasifier for performing the invention; and Fig. 2 shows a cross section of the gasifier shown in Fig. 1 taken at section A-A. 5. DESCRIPTION OF PREFERRED EMBODIMENT 15 Fig. 1 shows a fixed-bed pressure gasifier (1) and Fig. 2 shows a sectional representation of the plane A-A in top view. Fixed-bed pressure gasifier (1) comprises a pressure vessel (9) having at its top an inlet (2) for coarse-grained, solid fuels and a raw gas outlet (30). At the bottom 20 of a vessel (9), the fixed-bed pressure gasifier (1) has a rotary grate (5) for supplying first gasification media (6) for the non-slagging gasification and an ash discharge (31). In the upper part of the fixed-bed pressure gasifier, the fuel inlet (2) opens into a 25 hanging shaft (28). Beside the fuel inlet (2) for coarse-grained fuels, an inlet (21) for fine fuels is arranged at the top of the fixed-bed pressure gasifier (1). The fine fuel inlet (21) opens into a downpipe (22) held within the hanging shaft (28), wherein the downpipe (22) is longer than the hanging shaft (28) and ends in the reaction space of the fixed-bed pressure gasifier (1) with a baffle plate (24). The 30 fine fuel inlet is inertizable with nitrogen (27). The clear inside diameter of the vessel (9) of fixed-bed pressure gasifier (1) is 4 m and the height of the heap of the fixed bed (3), calculated from the tip (4) of the 17 rotary grate (5), is 6 m on average. It is defined by the hanging shaft (28) for fuel distribution. The heap of the fixed bed (3) ideal-typically is divided into the five layers, from bottom to top: first ash zone (14), first oxidation zone (15), first gasification zone (16), first pyrolysis zone (17) and first drying zone (18). 5 At a height of 3 m above the tip (4) of the rotary grate (5), there are provided ten stubs (7) for supplying the second gasification media (8) into vessel (9), for the slagging gasification of the fuel charge. Stubs (7) are uniformly distributed about the periphery of vessel (9) of the fixed-bed pressure gasifier (1). 10 Above the tip (4) of the rotary grate (5), in the upper plane of the first gasification zone (16) and above the first pyrolysis zone (17), an (additional) supply stub (7) extends through the wall of vessel (9). 15 The supply stubs (7) in the upper plane of the first non-slagging gasification zone (16) are equipped with gasification media nozzles (12) reaching into the gasification zone for the supply of second gasification media (8) for the slagging gasification. 20 In the sectional view of Fig. 2, the stubs (7) are numbered with /1/ to /10/ in clockwise direction. They are guided through the outer, pressure-bearing vessel wall (10) and through the inner steel jacket (11) of vessel (9). A total of six of the ten stubs (7) are equipped with gasification media nozzles (12). The gasification media nozzles (12) are designed as tubular nozzles, aligned radially and inclined 25 downwards with an angle of 150 against the horizontal. They extend 50 cm into the heap of the fixed bed (3). The orifices (13) of the gasification media nozzles (12) end in the upper region of the first non-slagging gasification zone (16). The stub (7) directed into the first drying zone (18) cooperates with a briquetting 30 press (32) for supplying compacted or briquetted fine fuels (21) into vessel (9). The fixed-bed pressure gasifier thus constructed is operated as follows: 18 In the fixed-bed pressure gasifier (1) 58 t/h of non-caking, coarse-grained hard coals (2) with an ash content of about 35 wl-% (dry), a water content of about 5 wt-% (dry), an ash melting point of about 1400 *C and a grain size of about 5 100 mm are gasified at a total pressure of about 30 bar. The hard coals (2) are 5 introduced into the fixed-bed pressure gasifier (1) from above. The raw gas (29) leaves the fixed-bed pressure gasifier (1) through the raw gas outlet (30), while the ash (31) is withdrawn at the bottom by means of the rotary grate (5). Via the rotary grate (5) the first gasification media (6) are supplied. The quantity of the first oxygen of the first gasification media is 12,000 Nm 3 /h (based on pure 10 oxygen), the steam/oxygen ratio is about 4.5 kg/Nm 3 on average. The quantity of the second oxygen of the second gasification media (8) in total is 3200 Nm 3 /h (based on pure oxygen), the steam/oxygen ratio is 0.8 kg/Nm 3 . 15 The gasification media nozzles (12) with the numbers /3/, /4/, /8/ and /9/ each are charged with 600 mSted/h of oxygen and the gasification media nozzles (12) with the numbers /1/ and /6/ each are charged with 400 metd 3 /h of oxygen. The second gasification media flow with flow velocities of 70 m/s (gasification media nozzles (12), numbers /3/, /4/, /8/ and /9/) and 50 m/s (gasification media nozzles (12), 20 numbers /1/ and /6/). Before the orifices (13), turbulent zones (19) are formed. Before the adjacent gasification media nozzles (12), numbers /3/ and /4/ as well as numbers /8/ and /9/ two larger, coherent regions (20) of the turbulent zones (19) are formed. 25 About centrally above the coherent regions (20) of the turbulent zones (19) of the adjacent gasification media nozzles (12), numbers /3/ and /4/ as well as numbers /8/ and /9/, fine fuels (21) are introduced gravity-fed via downpipe (22) or force fed via the stuffing inlet by means of the briquetting press (32). 30 Baffle plates (24) are located at the lower outlet opening (23) of the downpipe (22), below which cavities (25) are formed in the heap of the fixed bed (3) and into which the fine fuels (21) can flow off freely. The downpipe (22) is supported at the hanging shaft (28) with holders (26). The vertical distance of the outlet 19 openings (23) to the gasification media nozzles (12) is 2 m. The downpipe (22) can be inert with a small amount of nitrogen (27). The fine fuels (21) stem from the same hard coals used to charge vessel (9) via 5 top inlet (2). The grain size of the fine fuels (21) is 0 - 2 mm, the ash content is 40 wt.-% (dry), the water content 5 wt.-% (dry). Both downpipes (22) are supplied with 5.5 t/h of fine fuels (21) each. The thermal capacity of a fixed-bed pressure gasifier (1) incorporating the 10 process-based and/or constructional features of the present invention can be increased, in the present example, by about 25% compared with a gasifier that does not incorporate the invention's features. In addition, co-gasification of fine fuel becomes possible for the first time to a considerable extent.

20 Reference Numerals 1 fixed-bed pressure gasifier 2 inlet for coarse-grained, solid fuel 3 fixed bed 5 4 tip 5 rotary grate 6 first gasification media 7 stub 8 second gasification media 10 9 vessel 10 pressure-bearing vessel wall 11 inner steel vessel jacket 12 gasification media nozzles 13 orifices of the gasification media nozzles 15 14 first ash zone 15 first oxidation zone 16 first gasification zone 17 first pyrolysis zone 18 first drying zone 20 19 turbulent zone 20 coherent region 21 fine fuels 22 downpipe 23 outlet opening 25 24 baffle plate 25 cavities 21 26 holder 27 nitrogen 28 hanging shaft 29 raw gas 5 30 raw gas outlet 31 ash 32 briquetting press 33 agglomeration aid

Claims

1. A process for the fixed-bed pressure gasification of solid fuels with oxygen and steam-containing gasification media by means of a fixed-bed pressure gasifier with a feed for coarse-grained, solid fuels and with a gas draw, both at the 5 top of the fixed-bed pressure gasifier, with a rotary grate and with an ash discharge at the bottom of the fixed-bed pressure gasifier, with an adjustable feed for first gasification media for a non-slagging gasification by means of the rotary grate of the fixed-bed pressure gasifier, wherein critical minimum values for the steam/oxygen ratio can be adjusted, with a heap of the fixed bed above the rotary 10 grate, characterized in - that in addition to and independent of the first gasification media supplied by means of the rotary grate second gasification media for a slagging gasification are injected via at least one gasification media nozzle reaching into the upper region of the fixed-bed heap, 15 - and that the second gasification media are injected with steam/oxygen ratios of 0.5 to 4 kg/m 3 and gas exit velocities of 20 to 120 m/s.

2. The process according to claim 1, characterized in that the second gasification media are injected into a height zone of the fixed-bed pressure gasifier which maximally reaches from 1 m above the tip of the rotary grate to 0.5 20 m below the surface of the heap of the fixed bed.

3. The process according to claim I or 2, characterized in that coarse grained, solid fuels with a grain size greater than 2 mm are introduced into the fixed-bed pressure gasifier.

4. The process according to each of claims 1 to 3, characterized in that fine 25 grained and/or pulverized fuels are added to the turbulent zones which are formed before the gasification media nozzles, wherein the quantity of the added fine-grained and pulverized fuels at most is so large that in stoichiometric terms a substantial gasification in the turbulent zones is ensured. 23

5. The process according to each of claims 1 to 4, characterized in that the second gasification media alternatively are injected in two height zones each with a vertical extension of < 1 m, which have a minimum vertical distance of 1 m from each other and corresponding to the maximum and the minimum bed height of 5 the fixed bed of the fixed-bed pressure gasifier each are arranged in the upper half of the first gasification zone, below the pyrolysis zone. L'AIR LIQUIDE, SOCIETY ANONYME POUR L'ETUDE ET L'EXPLOITATION 10 DES PROCEDES GEORGES CLAUDE WATERMARK PATENT AND TRADE MARKS ATTORNEYS P39330AUOO